Abstract: A television receiver equipped for the display of data transmitted during the line flyback period and also for the display of data transmitted over the telephone via a modem is provided with circuitry for detecting the absence of the normal television synchronizing signals and for providing internal synchronizing to enable the continuance of the display of data.

Abstract: A receiver for a television transmission system of the kind in which some of the line scan periods of a conventional transmission that are left blank (as far as picture content is concerned) between successive frame transmissions are utilized for signalling data for selective display on the screen of a television receiver. The information to be displayed as a line of data may be transmitted in a single line scan period. This is achieved by transmitting in a line scan period a page number and then in subsequent line scan periods the lines of data for that page. New page numbers are then transmitted followed by their respective lines of data in sequence. The receiver selects a desired page of data by identifying the desired transmitted page number and then recording all lines of information subsequent to that page number until it identifies a further page number whereupon it ceases to store any further information.